1. Field of the Invention
The present invention relates to an illuminated push-button switch, and more specifically to an illuminated push-button switch which is illuminated at all times to indicate its location.
2. Description of the Prior Art
In conventional illuminated push-button switches, the lamp accommodated therein is typically turned on only when the push button is depressed. Therefore, when it is attempted to manipulate the push buttons in a dark place such as in an automobile at night, it is very difficult to find where the push buttons are located.
To eliminate the above defect, a variety of types of illuminated push-button switches have been proposed.
FIG. 1 is a section view illustrating a major portion of a known illuminated push-button switch such as that described in U.S. Pat. No 4,277,665, in which reference numeral 101 denotes a cap made of a synthetic resin, 102 denotes a display board made of a light-transmitting material. As shown in FIG. 2, for example, the display board 102 bears characters ON and OFF in colors complementary to each other, e.g. bluish green for ON, and red for OFF, with the remaining areas painted black. Reference numeral 103 denotes a front plate having a through hole 103a and a notched portion 103c in a side portion thereof, the notched portion 103c having a recess 103b. Reference numeral 104 denotes an operation member containing two sets of narrow tongue pieces 104a, 104a that are formed so as not to interrupt the transmission of light, and further having an operation arm 104b which protrudes from the side wall. The cap 101, display board 102 and operation member 104 are assembled together to form a push button 105. Reference numeral 106 denotes a rotary member consisting of two plates 107, 108 assembled at right angles to each other and which are rotatably supported by the front plate 103. Reference numeral 109 denotes a cover having a lamp 110 as a light source fitted to a hole 109a at a rear portion thereof. The cover 109 is attached to the front plate 103 by a screw. Reference numeral 111 designates a coil spring which is accommodated in the notched portion 103c of the front plate 103 and which powers the operation arm 104b of the operation member 104. The coil spring 111 has a resilient force that is smaller than the resilient force of a coil spring 113 which works to return a switch 112 that is provided with a self-locking mechanism.
Next, the operation of the thus constructed conventional illuminated push-button switch is described below.
FIG. 1(A) illustrates the case in which the push button has not been depressed. The light of lamp 110 passes through the red rotary plate 107 so red light reaches the display board 102. However, since the character ON is bluish green, the red light cannot pass therethrough and the character ON appears black. In this case, since the background is painted black, the character ON is not discernible. The character OFF, however, is red, so the red light can pass through and the character OFF is displayed in red on the display board 102.
When the push button 105 is depressed in the direction of arrow A as shown in FIG. 1(B), the tongue piece 104a of the operation member 104 comes into contact with the rotary plate 107 of the rotary member 106 that is supported by the front plate 103, whereby the rotary member 106 is rotated such that the bluish-green plate 108 is positioned in the path of the light from lamp 110 as shown in FIG. 1(C). At the same time, the operation arm 104b comes into contact with the switch 112 and the operation rod of switch 112 is depressed to actuate switch 112, which will be locked in position by a locking mechanism (not shown). Under this condition, the light of the lamp 110 passes through the bluish green plate 108; and bluish green light reaches the display board 102. However, the red character OFF does not pass bluish green light and appears black, and so is not indiscernable against the black background. On the other hand, the bluish green character ON passes the bluish green light and is displayed in bluish green on the display board.
If the push button 105 is depressed again, the switch 112 is liberated from the locked state, the rotary member 106 is rotated by the tongue piece 104a of the operation member 104, and the switch is actuated to return to the state of FIG. 1(A).
According to the above-mentioned conventional switch in which rotary plates having two complementary colors are interposed between the light source and the display board which displays the characters or symbols by relying upon the two complementary colors, it was possible to produce only a simple display such as ON and OFF. It was not possible to display the name of a device that is to be controlled by the switch, leaving much room for improvement.